The invention relates to starter drives for internal combustion engines, and more particularly to a shield for the rectangular springs in such starter drives.
Standard internal combustion engines generally utilize an electric starting motor with a starter drive having a roller overrunning clutch structure of the type referred to in U.S. Pat. No. 3,830,406 issued June 28, 1974 to Toulier. Such a starter drive has a pinion gear for mating with the flywheel of the engine to be started. The starter drive has a sleeve which is mounted on the shaft output of the starter motor and which is connected to the driving portion of the clutch. The driven portion of the clutch is connected to the pinion gear. The driving portion of the clutch is annular around and concentric with the driven member. A number of cylindrical rollers are housed in tapered recesses formed in the driving member. Each roller is wedged against the wall of the recess and the outer cylindrical surface of the driven member when the driven member is rotated by the starter motor, and is biased away from the wedging position by a rectangular spring when the pinion gear overruns the driving member. In this way, the starter motor can drive the pinion gear when it is meshed with the flywheel of the engine to be started, but will allow the flywheel to overrun the starter motor when the engine has been started. Rectangular rather than circular springs are required to effectively engage the sides of the cylindrical rollers.
The most common reason for failure of such starter drives is the failure of the rectangular springs. The constant flexing of the springs under pressure eventually causes failure of the springs and seizing of the starter drive which in turn can cause damage to the starter motor and generally requires repair and replacement of the starter drive. In the Toulier U.S. Pat. No. 3,820,406, there is suggested the replacement of the rectangular springs with a pair of circular springs used in conjunction with a guide and a base plate. However, this design cannot be used with the existing springs of standard starter drives, and it requires at least four parts to replace each spring. There is therefore a need for a simple means of improving the performance of the rectangular springs in existing starter drives.